1. Field of the invention
This invention relates, generally, to the medical arts. More particularly, it relates to a method for endoluminal installation of a stent graft.
2. Description of the prior art
Stent grafts are used to hold arteries open so that blood may flow therethrough. They also have utility in treating aneurysms, in effect replacing an artery where the walls of the artery have ballooned outwardly and are in danger of rupturing. Stent grafts are formed of materials that are inert to the human body so that they may be left in place indefinitely. The materials from which stent grafts are made are highly flexible so that they may be compressed into a small space such as a lumen of a catheter. The materials are also highly resilient, i.e. , have excellent memory, so that when a stent graft is pushed out of the lumen of a catheter, it expands under its inherent bias to its operable size.
Tubular stent grafts are relatively easy to deploy in straight sections of arteries. However, there are areas of the body where deployment is problematic because a tubular stent graft cannot be used. A section of the abdominal artery, just slightly upstream of where it divides into the left and right iliac arteries, also known as the left and right common iliac arteries, is prone to the development of aneurysms and is a location where a tubular stent graft has no utility.
The stent graft that has been developed for this problematic area of the abdominal artery is often described as looking like a pair of pants having a waist part with one long leg and one short leg depending therefrom. When properly deployed, the waist part and the short leg thereof are positioned within the aneurysm of the abdominal artery, just downstream of the renal arteries. The long leg has a trailing end disposed within a first common iliac artery. If the short leg were also elongate and if its trailing end could easily be fitted into the second common iliac artery, then the positioning of a stent graft in an abdominal artery aneurysm would not be problematic.
Deploying a stent graft in an abdominal artery aneurysm so that blood can flow through the stent graft and avoid putting pressure on the ballooned arterial walls is difficult because the waist part of the stent graft must be positioned within the abdominal artery, and the left and right legs of the stent graft must fit into the left and right common iliac arteries, respectively.
There are two basic designs for endoluminal stents having utility in the repair of abdominal aortic aneurysms. Two. elongate legs are provided in the first design. A first leg is positioned in the first iliac artery and a second leg is pulled into the second iliac artery to form an inverted xe2x80x9cYxe2x80x9d configuration. The present invention pertains to the second design where the stent includes a long leg and a short leg. An extension for the short leg is manufactured as a separate piece and is known as a contralateral limb because it is laterally opposed with respect to the first elongate leg of the stent graft. The physician inserts the contralateral limb into the short leg, thereby creating a conduit from the stent to the contralateral iliac artery and excluding blood flow from the aneuryismaneurysm.
Thus, in the second design, an extension for the short leg must be manufactured as a separate piece, and the physician must insert the extension for the short leg into the second iliac artery and try to secure it to the short leg.
The method most commonly employed to join a contralateral limb to the short leg of a stent graft is to introduce the contralateral limb through an incision in the patient""s leggroin. More particularly, the contralateral limb is endoluminally introduced through a common femoral artery. The leading end of the contralateral limb is inserted into the trailing end of the short leg of the stent graft and the trailing end of the contralateral limb is left in the second common iliac artery to complete the installation.
There are several drawbacks to this approach, but the primary drawback is that it requires a physician to correctly aim the leading end of the contralateral limb at the trailing end of the stent graft short leg. This is a very difficult task under fluoroscopy or other imaging technique. What might look like a perfect connection may be a complete miss. For example, if the leading end of the contralateral limb goes directly underneath the trailing end of the short leg of the stent graft, it will appear to the physician performing the procedure that the alignment is perfect and that the job has been successfully completed. The results of such a misalignment are catastrophic.
What is needed, then, is an improved method for endoluminally introducing the leading end of a contralateral limb into the trailing end of the short leg of a stent graft.
However, in view of the prior art considered as a whole at the time the present invention was made, it was not obvious to those of ordinary skill in the pertinent art how such need could be fulfilled.
The long-standing but heretofore unfulfilled need for an improved method for installing a contralateral limb to a stent graft in the area of an abdominal artery aneurysm is now met by a new, useful, and nonobvious invention. The novel method includes the steps of inserting a first guide wire through an incision endoluminally into a first common femoral artery and pushing the first guide wire into the abdominal artery until a leading end of the first guide wire extends beyond a leading end of the stent graft. A first sheath is endoluminally introduced into an elongate leg of the stent graft, using the first guide wire to guide the first sheath into the elongate leg. The elongate leg has a trailing end received within the first iliac artery. The first guide wire is then removed from the sheath. A first catheter having a return bend formed near its distal end and having a first magnet means mounted to the distal end is introduced into a lumen of the first sheath. The first catheter is pushed into the first sheath until the return bend emerges from the lumen of said first sheath. The first catheter is then displaced in a distal-to-proximal direction, relative to the incision site, until the first magnet means emerges from the hollow interior of the stent graft and into the interior of the aneurysm. A second catheter having a second magnet means on a distal free end thereof is introduced into a second, opposite femoral artery and positioned near the first magnet means so that the first and second magnet means (having a polarity opposite to that of the first) are attracted to one another. The second catheter is then pulled into the hollow interior of the stent graft. A second guide wire is then introduced into the lumen of the second catheter until the distal free end of the second guide wire has extended completely through the second catheter and through the stent graft. The first and second catheters are then removed. A second sheath is introduced over the second guide wire until the distal free end of the second sheath has entered the hollow interior of the stent graft. A contralateral limb is then introduced through the second sheath until the distal free end of the contralateral limb has extended from the second sheath and entered into the hollow interior of the stent graft. The contralateral limb deploys under its inherent bias so that it expands in diameter. The second sheath is then withdrawn and blood flows into a first end of the. stent graft and out the bifurcated lower end thereof into the left and right iliac arteries.
The steps of the novel method may also be performed with a modified version of the first catheter. An opening is formed in the distal end of the first catheter in close proximity to the first magnet means secured to the distal end of the first catheter. The opening may also be formed in close proximity to the reverse bend formed in the first catheter. A guide wire extends through the first catheter from its proximal end and exits through the opening. This configuration minimizes the profile of the first catheter by placing the magnet therewithin instead of on the outside of the first catheter and thus dedicates the lumen of the first catheter to the guide wire. Moreover, the guide wire provides additional support for pushing the catheter cephalad beyond the leading end of the stent graft. After the catheter is advanced over the guide wire, the guide wire is withdrawn into the straight part of the first catheter proximal to the reverse bend or the guide wire is completely removed from the lumen.
The step of removing the first and second catheters is accomplished by pulling on the second catheter until the magnetic coupling between the first and second magnet means is overcome.
In an alternative embodiment, an opening is formed in a first straight-in-configuration catheter near its distal end. A pull string extends through the first catheter from its proximal end and exits the first catheter through said opening. The distal end of the pull string is secured to a first magnet means mounted on the distal end of the first catheter, or to the catheter in very close proximity to the first magnet. Pulling on the pull string thus forms a return bend in the distal end of the first catheter and positions the first magnet to a position where it can be more easily connected to a second magnet at the second end of a second catheter that is introduced through the contralateral limb.
In another alternative embodiment, a magnetic band having a polarity opposite to that of the magnet secured to the distal end of a first catheter is secured to the distal end of a second sheath. This eliminates the need for a second catheter. After the magnets have been coupled to one another, the sheath is pulled and pushed into the hollow interior of the stent graft. A deployment system is then employed to facilitate introduction of the contralateral limb through the second sheath. This eliminates the need for a second guide catheter, thereby shortening procedure time.
In another application of the invention, a nephroureteral stent is removed from a kidney by mounting a first magnet or ferromagnetic means to a first end of a nephroureteral stent that extends from a bladder to a kidney through a ureter. A second magnet means having a polarity opposite to a polarity of the first magnet means is mounted on the distal free end of a catheter and the distal free end of the catheter is introduced into the bladder through the urethra. The second magnet means is brought into close proximity with the first magnet means so that the first and second magnet means enter into a magnetic coupling with one another. The catheter is then withdrawn through the urethra, thereby pulling the first magnet means and hence the nephroureteral stent with it.
An alternative embodiment of the invention comprises the addition steps of threading a pull string through said catheter, said pull string having a first end and a second end, establishing a string aperture proximate to said first magnet, securing said first end to said catheter coincident to said first magnet whereby retraction of said second end draws said first magnet toward said string aperture thereby forming said return bend.
In all embodiments, one of the magnet means may be provided in the form of a ferrous material that is secured to the distal end of its catheter. For example, a ferrous metal band may be strapped onto the end of a catheter.
The primary object of this invention is to provide a method whereby a contralateral limb is attached to the short leg of a stent graft without requiring a physician to visually guide the contralateral limb into the short leg.
A closely related object is to provide a method that harnesses magnetism to facilitate the steps of the-method.
These and other important objects, advantages, and features of the invention will become clear as this description proceeds.
The invention accordingly comprises the features of construction, combination of elements, and arrangement of parts that-will be exemplified in the description set forth hereinafter and the scope of the invention will be indicated in the claims.